The invention relates to a tile particularly for installation on a sloping roof, but the tile could have applications elsewhere, for example on a vertical wall.
Interlocking roof tiles or shingles have been known for many years, and are commonly found as two main types, namely relatively thick clay tiles, or sheet tiles, which are made from sheet metal or other similar thin material. The clay tiles are heavy, mechanically relatively weak and are limited in mechanical complexity due to manufacturing difficulties and material limitations. Metallic sheet tiles also have problems, for example a tendency to bend and be permanently deformed after a person has walked over the roof, which is aggravated by insufficient backing support for the tile. Also, if a relatively thin material is used, the tile might lack adequate stiffness to resist bending under strong wind forces blowing up the roof and bending the tile upwardly, thus permitting water to penetrate under the tile. While attempts have been made to stiffen relatively thin tiles using several raised ribs extending between edges of the tile, commonly the ribs increase difficulty of installation of the tile because some designs of tile do not permit much variation or tolerance to the "fit" between overlapping portions of adjacent tiles, particularly when installed on uneven roofs. Commonly, with prior art ribbed metallic tiles, fitting errors during installation of a series of tiles can accumulate to such an extent that unsightly gaps can exist between overlapping portions of adjacent tiles, which can permit entry of water into the roof. In general the more complex the ribbed structure of the overlapping portions, the greater the difficulty and cost of manufacture and installation.
Typical metallic tiles are shown in U.S. Pat. Nos. 279,487 issued to Jones; 294,256 issued to Montross et al; 361,031 issued to Thorn; 397,298 issued to Lee; 403,837 issued to Gusten; 562,798 issued to Brocker and 2,202,830 issued to Bussey. These patents disclose metallic roofing tiles with ribs to cooperate with adjacent tiles, and partially to stiffen the tile. However, some of the immediate edge fitting structure includes the actual ribs themselves, and these are quite complex and would likely present difficulties when installing the tiles. Ribs provided immediately adjacent edges of the tiles without flat side margins extending to the edges can present difficulties during the manufacture and installation and can present difficulties during inclement weather.
In general, to produce a tile of a given size, tiles with several ribs or corrugations require considerably more sheet stock or raw sheet material than a flat, unribbed tile or a tile with fewer ribs. Also, some tiles require a relatively wide overlap with adjacent tiles to obtain a water tight joint, and this affects the number of tiles required to cover a specific roof area with tiles of a given size. Clearly the greater the overlap between tiles, the more tiles are required to cover a given roof area. Some prior art tiles have many corrugations and also require a large overlap and thus the effectiveness of such tiles for covering area is low.
Some of the prior art tiles have interfitting edge portions which cooperate closely with complementary edge portions of adjacent tiles such that relatively small gaps of short lengths exist between the tiles. There gaps can be of such a size as to cause water to be drawn by capillarity effects through the gaps, around the ribs and into the roof, which can resemble leaks from a leaking roof. The ribs and/or edges of most prior art tiles are asymmetrical and thus cannot be trimmed and reversed easily for fitting in confined spaces, or to reduce wastage of tile portions. Also, some tiles do not lend themselves to easy vertical stacking and thus can be awkward to transport or store.